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Biomedical subjects

D F Anderson

Publications and source records attributed to D F Anderson.

At least 19 recordsLinked to original sources
PubMed1999

Regulatory response of intramembranous absorption of amniotic fluid to infusion of exogenous fluid in sheep.

Six fetal sheep were operated on at 118 to 121 days of gestation. The pulmonary end of the trachea was connected to the gastric end of the esophagus with a section of tubing. This left urine as the only source of amniotic fluid and intramembranous absorption as sole exit. Multiple indwelling fetal vascular, intra-amniotic, allantoic, and a fetal bladder catheter were placed. Beginning 5 days after surgery, all urine was drained from the bladder and immediately reinfused into the amniotic sac to monitor urine production rate. After 4 days of urine infusion alone, the urine infusion was augmented for 6 days with an intra-amniotic infusion of Ringer solution. Amniotic and allantoic fluid volumes were measured at autopsy. During the period of Ringer infusion, intramembranous absorption of amniotic fluid increased by more than 1,191 +/- 186 (SE) ml/day (P < 0.002) and the rates of Na(+) and Cl(-) absorption increased to more than five times (P < 0.005) and eight times (P < 0.005) their initial values. Only one of six fetuses had polyhydramnios. It is concluded that intramembranous absorption of amniotic fluid makes a strong regulatory adjustment in response to an abnormal increase in inflow of exogenous fluid.

Absorption↗
PubMed1999

Non-communication between ophthalmologists and optometrists.

Many patients seen in the British hospital eye service are referred by high-street optometrists; and, if the optometrist is to receive feedback from the ophthalmologist, the patient should consent to disclosure of medical information. On the referral form (revised GOS 18) there is a space for this purpose. We investigated the level of communication by asking optometrists in our hospital catchment area about their use of the GOS 18 form and by examining the medical records of all new patients seen in the eye outpatient department in one month. 79 optometrists (55%) returned the questionnaire. 54 routinely used the GOS 18; and, of these, 10 said they obtained patient consent always, 23 sometimes and 21 never. 158 of 555 sets of medical notes contained an optometrist's referral, 107 of them on the revised GOS 18; and patient consent had been recorded on 17 of these forms. Ophthalmologists responded to the optometrist in 2/17 (12%) cases where consent had been obtained and 15/90 (17%) where it had not. Ophthalmologists could provide much better feedback to optometrists. The GOS 18 form could be used more effectively; and there is no reason why patient consent to disclosure of medical information should not be obtained by ophthalmologists as well as by optometrists.

Communication↗
PubMed1998

Human mast cells express stem cell factor.

Stem cell factor (SCF) is a major cytokine regulator of mast cell growth and function. The present study demonstrates that human mast cells are able to produce SCF. Constitutive synthesis of SCF mRNA was seen in the mast cells isolated from human lung and skin by RT-PCR. This was confirmed by in situ hybridization in conjunctival mast cells of both tryptase-only (MCT) and tryptase/chymase (MCTC) subsets. SCF protein product was found in conjunctival MCT and MCTC mast cells by immunohistochemistry. Soluble SCF protein was detected in the culture supernatant of isolated lung mast cells by ELISA, and cross-linkage of IgE receptor (Fc epsilon-RI) on the lung mast cells in culture did not alter SCF mRNA expression, or the secreted soluble SCF protein. This was consistent with the finding that levels of SCF mRNA expression in conjunctival mast cells were similar between normal subjects and patients with seasonal allergic conjunctivitis (SAC). This study shows that human mast cells themselves are a cellular source of SCF, as well as being target cells for this growth factor. SCF may regulate mast cell growth and function via both paracrine and autocrine mechanisms. The production of SCF by mast cells may be regulated via mechanisms other than IgE receptor-mediated pathways.

Cell Culture Techniques↗
PubMed1998

Direct ophthalmoscopy versus slit lamp biomicroscopy in diagnosis of the acute red eye.

The causes of red eye range from trivial to life-threatening, and many general practitioners are uncertain of their ability to diagnose them with the aid of an ophthalmoscope. We tested the hypothesis that, in the assessment of a patient with red eye, a doctor using a slit lamp biomicroscope would not differ in diagnostic accuracy from a doctor using a direct ophthalmoscope. A cross-over study was conducted in 98 patients newly attending an eye casualty department. 71% of diagnoses agreed exactly, and all potentially sight-threatening lesions were either diagnosed correctly or managed appropriately by doctors using an ophthalmoscope. We conclude that the initial diagnosis and management of patients with an acute red eye is not prejudiced by the lack of a slit lamp biomicroscope.

Acute Disease↗
PubMed1998

Adhesion molecules and relationship to leukocyte levels in allergic eye disease.

PURPOSE: To evaluate the conjunctival expression of leukocyte cell adhesion molecules (CAMs) and their relationship to leukocyte patterns on the microvasculature in the different clinical subtypes of allergic eye disease. METHODS: Immunohistochemical analysis, using appropriate monoclonal antibodies, was applied to glycolmethacrylate-embedded biopsies of bulbar and tarsal conjunctival tissue. The proportion of total blood vessels expressing a particular CAM was derived and related to individual cell types identified by cell-specific markers, such as mast cells, eosinophils, neutrophils, T cells, and macrophages. Statistical analysis was used to correlate adhesion molecule expression and, ultimately, cell type. RESULTS: There was a basal expression of intercellular adhesion molecule-1 (ICAM-1) (21% bulbar, 18% tarsal), E-selectin (15% bulbar, 21% tarsal), and vascular cell adhesion molecule-1 (VCAM-1) (13% bulbar and tarsal) in normal controls. In seasonal and perennial (bulbar and tarsal conjunctival) allergic tissue, ICAM-1 and E-selectin were expressed in 40% to 78% of vessels; in chronic disease, they were expressed in 45% to 80% of vessels; and in vernal giant papillae, they were expressed in as many as 90% of vessels. There was also increased expression of endothelial VCAM-1 in all forms of allergic eye disease; the greatest values were found in vernal giant papillae (64%). Biopsies taken in winter from seasonal sufferers demonstrated a marked reduction in levels of all three CAMs compared with those taken in the pollen season. This is almost consistent with values found in normal conjunctiva. Positive correlations were found between the levels of ICAM-1 and E-selectin expression and the degree of granulocyte and lymphocyte infiltration, although VCAM-1 expression correlated most closely with eosinophil numbers. CONCLUSIONS: Increased levels of cell adhesion molecules on the microvasculature and the factors that regulate them are likely to be responsible for the infiltration of cells bearing their ligands and may perpetuate inflammation in the chronic forms of allergic eye disease.

Adult↗
PubMed1997

Coronary heart disease risk factors in employees of Iowa's Department of Public Safety compared to a cohort of the general population.

The prevalence of coronary heart disease (CHD) risk factors in law enforcement personnel compared to that in the general population was studied by determining the predicted 10-year risk for developing CHD (CHD10, expressed as %) in subjects from the Iowa Department of Public Safety and comparing it to the average CHD10 for similarly aged subjects in the Framingham Heart Study cohort. The Iowa data included measures on 388 men from 30 to 64 years old, 246 of whom were measured in 1980-1981 and again in 1992-1993. The CHD10 came from an algorithm developed using the Framingham data; it included measures of age, gender, cholesterol, HDL-C, systolic blood pressure, smoking habit, glucose level, and left ventricular hypertrophy (ECG criteria). For this group, average CHD10 was reported by age in five-year increments [Circulation 83:356, 1991]. The Iowa subjects (n = 388) did not show a statistically significant difference in CHD10 from the reference population (8.9% versus 7.9%). The change with age was very similar in the two groups: for Iowa (n = 388) the estimate was CHD10 = -16.5 + .59 (age); for Framingham it was CHD10 = -17.5 + .60 (age). The change in individual risk factors with time was also similar in both groups; the per year change in CHD10 in the Iowa subjects, which was measured twice (n = 246, 0.63%), did not differ statistically from the 0.60% change predicted by the Framingham model. These results suggest that, for the risk factors considered here, the 10-year probability of developing CHD among Iowa law enforcement personnel is similar to that found in the Framingham population.

Adult↗
PubMed1997

Angiotensin mediated interaction of fetal kidney and placenta in the control of fetal arterial pressure and its role in hydrops fetalis.

Fetal cardiovascular control is effected by an interaction of the fetal somatic and placental circulations. Three primary regulatory mechanisms are involved: transplacental transfer of extracellular fluid, driven by a difference in hydrostatic and oncotic pressures; modulation of fetal placental and somatic vascular resistances by means of blood pressure controlled production of angiotensin; and somatic autoregulation of flow. A systems analysis incorporates these and other fetal cardiovascular functions and this analysis was modelled for computer simulation. Given physiologically plausible values for known cardiovascular parameters in the fetal sheep, the model reproduced in detail a variety of experimental protocols with known outcomes; these included the normal fetus, the fetus after bilateral nephrectomy, the nephrectomized fetus infused with angiotensin, the intact fetus infused with NaCl solutions, the fetus with lymphatic obstruction and the severely anaemic fetus. The systems analysis demonstrated that fetal cardiac failure constituted the strongest stimulus for the formation of fetal oedema of any tested pathological intervention.

Angiotensin II↗
PubMed1997

Seasonal allergic conjunctivitis is accompanied by increased mast cell numbers in the absence of leucocyte infiltration.

BACKGROUND: Seasonal allergic conjunctivitis (SAC) is the most common allergic disease to affect the eye, occurring alone or in association with allergic rhinitis. Infiltration with mast cells and eosinophils is characteristic of the chronic forms of allergic conjunctivitis such as vernal and atopic keratoconjunctivitis, and these cell types also contribute significantly to allergic inflammation in the skin. Indirect evidence for a similar pattern of cellular events in SAC comes from studies which demonstrate raised eosinophil and neutrophil numbers in conjunctival scrapings and elevated levels of mast cell tryptase in tears following allergen challenge. OBJECTIVE: To directly characterize the inflammatory cell infiltrate in SAC and to determine its clinical relevance. METHODS: We employed specific immunohistochemical staining to count mast cells, eosinophils and neutrophils in the conjunctival epithelium and lamina propria of eight atopic patients with SAC in, and 12 SAC patients out of the hay fever season. Sixteen patients with no history of ocular allergy were used as control subjects. RESULTS: Mast cells were absent from normal epithelium. During the pollen season median mast cell numbers in the lamina propria were found to be increased by 61% in patients with SAC compared with normals (P=0.012). Eosinophils were found in the lamina propria in less than half of the symptomatic patients with SAC and in only three patients were eosinophils present in the epithelium. The neutrophil numbers in the lamina propria of patients with SAC tended to be higher than normals but these changes did not reach statistical significance. CONCLUSION: These data based on the direct assessment of conjunctival tissue provide evidence that symptoms occur in SAC in the absence of detectable recruitment of eosinophils or neutrophils. This suggests that this disorder is related to mast cell-mediated changes.

Adult↗
PubMed1997

Predictive factors for the development of rubeosis following proton beam radiotherapy for uveal melanoma.

AIMS/BACKGROUND: Proton beam radiotherapy can effectively treat primary uveal melanomas of any size. Some patients, however, develop adverse late effects following treatment and the purpose of this study was to determine which factors give rise to a poor local outcome. METHODS: The hospital records from a first cohort of 127 patients treated by protons from 1989 to 1992 were reviewed retrospectively. The presence of rubeosis was selected as a measure of significant ocular damage. Split file analysis was performed with 73 cases forming a test group with the remaining 54 cases acting as a validation group. RESULTS: Large tumour size and the presence of retinal detachment were significant, independent risk factors for developing rubeosis for both the test and validation groups. These factors also predicted subsequent enucleation for uncontrolled ocular pain. Patients with tumours too large to plaque and with an associated retinal detachment had a 90% chance of developing rubeosis within 4 years of proton beam radiotherapy. CONCLUSIONS: Patients with a uveal melanoma too large for plaque therapy and an associated retinal detachment run a very high risk of developing rubeosis after proton beam radiotherapy and one third of individuals developing rubeosis required enucleation for pain even if local tumour control was satisfactory.

Adult↗
PubMed1997

Immunolocalization of cytokines to mast cells in normal and allergic conjunctiva.

BACKGROUND: Recently, the potential role of mast cells in allergic reactions has been extended by the discovery that these cells synthesize, store and secrete multifunctional cytokines. Seasonal allergic conjunctivitis is characterized as an immediate hypersensitivity reaction, in which allergen binds to specific IgE on mast cells, leading to release of pre-formed and newly synthesized inflammatory mediators. OBJECTIVE: In this study we aimed to localize the cytokines IL-4, IL-5, IL-6, IL-8 and TNF alpha to conjunctival mast cells and to examine the relationship between mast cell-associated cytokines and allergic conjunctivitis. METHODS: Immunohistochemistry was performed on serial sections of conjunctival biopsies from patients with seasonal allergic conjunctivitis, in and out of the hay fever season, as well as from non-allergic volunteers. RESULTS: IL-4, IL-5, IL-6 and TNF alpha were localized to mast cells in normal and allergic conjunctiva. IL-8 was localized to mast cells in two patients with seasonal allergic conjunctivitis, one during and the other outside the pollen season. Using the monoclonal antibody 3H4, which identifies the secreted form of IL-4, biopsies from patients with active seasonal allergic conjunctivitis contained a significantly higher proportion of mast cells positive for IL-4, than those from out-of-season patients (P=<0.016). There was no difference between the two groups in the number of mast cells immunostained by the antibody 4D9 which identifies the stored form of IL-4. CONCLUSIONS: These results suggest that conjunctival mast cells can store a range of multifunctional cytokines and release IL-4 during active disease, which may give them an important role in upregulating allergic inflammation in the conjunctiva.

Adult↗
PubMed1995

Concentrations of Na+ and Cl- in transplacental ultrafiltrate in sheep.

1. Maternal blood was made transiently hypertonic by rapid I.V. infusion of a concentrated mannitol solution into pregnant ewes bearing lambs with an indwelling flow sensor and vascular catheters. 2. The transplacental flows of water and of Na+ and Cl- were calculated from the umbilical arteriovenous differences in the concentrations of 125I-labelled albumin and electrolytes, and the fetal placental blood flow. 3. The reflection coefficients of Na+ and Cl- were calculated by means of the Patlak equation and found to be 0.85 +/- 0.04 and 0.68 +/- 0.04 (means +/- S.E.M.). The filtration coefficient was 1.02 x 10(-7) +/- 0.12 x 10(-7) cm5 dyne-1 s-1. 4. The results fitted best to an equivalent pore radius in the placental barrier smaller than the currently accepted 0.44 nm but not less than 0.35 nm.

Animals↗
PubMed1995

Excess extrafetal fluid without demonstrable changes in placental concentration gradients after week-long infusions of angiotensin into fetal lambs.

It is known that a week-long infusion of angiotensin into fetal sheep produces polyhydramnios. The purpose of the present experiments was to determine whether an increased osmotic force across the placental barrier could account for the excess transfer of water. Six fetuses with indwelling catheters were infused with angiotensin-I and one with angiotensin-II; all, except one fetus in the first group, developed gross polyhydramnios. None of the transplacental concentration differences of the small plasma solutes Na+, Cl-, HCO3-, K+, urea, or glucose showed a demonstrable change and the same was true of the transplacental difference in freezing point osmolality and for the transplacental difference in plasma protein concentration. It is concluded that the infusion of angiotensin at a low dose rate is a reliable protocol for producing polyhydramnios. However, the present findings lend no support to the hypothesis that a primary change in transplacental osmotic force is the cause of the increased transplacental water transfer in this form of polyhydramnios. Alternative hypotheses are discussed in the light of recent discoveries.

Angiotensin I↗
PubMed1994

Relationship between physical activity and risk factors for cardiovascular disease among law enforcement officers.

This investigation examined the associations between exercise habits, measures of physical fitness, and 10-year cardiovascular disease risk (CVD10, expressed as %) among 470 law enforcement officers of differing ages (range = 21 to 63 y). Only 32% of this group exercised regularly (> or = 3 days/week, > or = 20 min/session, > or = preceding 4 weeks). Only exercising subjects > 48 years old exhibited a significantly (P < .01) lower 10-year risk of a CVD event than their inactive peers (12.2 +/- 5.6 vs 16.3 +/- 6.9%, mean +/- SD). At all ages, the peak oxygen consumption per unit time was higher (50.1 +/- 6.7 vs 44.8 +/- 6.1 mL.kg-1.min-1) in the exercising than in the nonexercising group. Exercising subjects < or = 36 years old were significantly (P < .05) leaner than nonexercisers (16.3 +/- 5.5 vs 19.6 +/- 5.5% body fat, respectively) and had greater muscular endurance (45 +/- 9 vs 40 +/- 9 60-s sit-ups, respectively). These data suggest that exercise reduces CVD risk by modifying major CVD risk factors only in law enforcement officers > 48 years old.

Adult↗